In this contribution, we explore the impacts of collective neutrino oscillations on the neutrino signals in the light of collapsar models of long-duration gamma-ray bursts (GRBs). Based on our collapsar simulations with three different precollapse angular momentum, we estimate the emergent neutrino spectra with or without the collective neutrino oscillations. To mimic the collective effects, we manually swap the neutrino spectra as a first step. In the case of an inverted mass hierarchy with a

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... mall mixing angle (sin 2 2θ 13 = 10 −4 ), we show that the event numbers of neutrinos could increase by a factor of 5 due to the spectral swap. By a currently planned Mton-class detector, we point out that the neutrino signals, sharply depending on the angular momentum of the collapsing stars, could be directly visible for a 10 Mpc distance scale. For a progenitor with smaller initial angular momentum, the neutrino signals could show a sudden disappearance, which coins the epoch when the accretion disk whose thermal pressure is carried away by neutrinos, is absorbed into the black hole. These signatures, if observed, could provide us a new astrophysical information to unveil the collapsar dynamics. 11th Symposium on Nuclei in the Cosmos, NIC XI